Mac users with Excel- help!

The girlfriend has a Macbook and is trying to change the names of her variables in the legend- when she clicks it it just comes up with the option to change the colour of the variable's points and line.

Apparently it's totally different to how it works on a PC- I know how to do it on a normal computer, but Office for Mac isn't the same.

If it's anything like Excel 2008 that i'm running, here's how I did it:

You need to label the data sets you're using, and it'll appear in the Legend. You can do that by clicking on Edit in the Chart Data bit of the formatting palette in the toolbox. That'll bring up a window much like that in the Windows version, where it shows where the data used to plot the chart is coming from, and one of the boxes there is "Name". Pop what you want in there and it should change the legend too.